Automatically steered self-propelled vehicle

ABSTRACT

A self-propelled vehicle is automatically reversed and steered to a new path if sensors thereon sense an obstruction surrounding an area, or an obstacle in the area so that the vehicle moves forward, rearward and laterally over the entire unobstructed area for treating the same with a tool, such as a brush or agricultural implement. The forward and rearward movements are maintained along straight paths independently of irregularities prevelant in the area, tolerances in the steering control system of the vehicle or other such influences.

ted States Patent 1191 1111 3,744,586 Leinauer July 10, 1973 [54]AUTOMATICALLY STEERED 2,750,583 6/ I956 McCullough l80/79.I XSELILPROPELLED VEHICLE 2,996,621 8/1961 Barrett 180/791 X 3,43l,9963/1969 Giles et al. l80/98 [75] Inventor: Erich Lelnauer, 3,669,2086/l972 Brooke 180/98 Ludwigsburg, Germany 3,152,3l7 10/1964 Mayer340/104 X [73] Assignee: Robert Bosch Gmbll, Stuttgart, FOREIGN PATENTSOR APPLICATIONS 920,881 3/1963 Great Britain l80/79.l

[22] Filed: Oct. 5, 1971 Primary ExammerBen amm Hersh pp N05 186,678Assistant Examiner-Lcslie J. Paperner Attorney-Michael S. Striker [30]Foreign Application PriorityData 7' '7 0m. 7, 1970 Germany P 20 49 136.5[57] ABSTRACT A self-propelled vehicle is automatically reversed and[52] US. Cl 180/79.1, 180/98, 250/202, steered to a new p if Sensorsthereon Sense an 340/282 343/7 5]) struction surrounding an area, or anobstacle in the [51] Int. (:1. B6211 1/24 area 89 that the vehicle movesforward, rearward and [58] Field 01 Search ISO/79.1, 98; laterally overth ntir unobstructed area for treating 313 5 7; 340 2 2; 250302; 343 75]) the same with a tool, such as a brush or agricultural implement. Theforward and rearward movements are 5 References Ci d maintained alongstraight paths independently of irreg- UNITED STATES PATENTS ularitiesprevelant in the area, tolerances in the steering 3,513,931 5 1970Warner et al 180/98 control System of the Vehlcle or other suchmfluences' 3,095,939 7/1963 Hine l80/79.l 11 Claims, 7 Drawing FiguresSHEEI10F4 PAIENTEUJULIOIQYS PAIENIEUJUL 1 0197s 3 5 sum 2 or a Fig. 3 5348 13 52a 48 35 36 37 38 39 40 41 L2 L3 L4 1.5

PAIENTEUJUUOIQYS sumuom AUTOMATICALLY STEERED SELF-PROPELLED VEHICLECROSS-REFERENCE TO RELATED APPLICATION The apparatus of the presentinvention constitutes an improvement over and a further development ofapparatus disclosed in the copending application Ser. No. 137,354 filedby Wolfram Miiller on Apr. 26, 1971 and owned by the assignee of thepresent case.

BACKGROUND OF THE INVENTION The present invention relates to an unmannedvehicle for treating the unobstructed part of an area havingobstructions preventing continued movement of the vehicle.

Vehicles of this type are known which move along guiding conductorsgenerating an alternating field. The actual path of the vehicle isdetermined by the guiding conductors, and the vehicle is incapable ofrecognizing obstructions which are ocated in the path of movementdetermined by a conductor, which was placed there after the operation ofthe vehicle was started. Since the guiding conductors are usually underthe floor, a changing of the path is not easily possible. Thearrangement of the prior art is unsuitable under conditions where loadsare deposited at varying and different places, as may occur in storageareas and warehouses. It may occur, that a truck deposits its load on aconductor, so that the vehicle, moving along the guiding conductor,would ram the load.

An apparatus which solves the above-mentioned problems is disclosed andclaimed in US. Pat. application Ser. No. 137,354 filed by WolframMi'iller on Apr. 26, 1971 and assigned to the assignee of the presentinvention. The apparatus disclosed in this referenced application is notlimited or dependent in the provision of guiding conductors which areusually placed under the ground. As described in that application, oncethat apparatus has selected a straight path to traverse, it proceedsessentially along said straight path. However, because of irregularitiesin the ground over which the vehicle passes, tolerances in the steeringmechanism and- /or other such influences, it is possible that thevehicle deviate off its selected straight path.

SUMMARY OF THE INVENTION It is one object of the invention to provide anautomatically steered self-propelled vehicle which does not have thedisadvantages of the vehicles known in the prior art.

Another object of the invention is to provide an automatically steeredself-propelled vehicle which will in a simple and effective way maintainthe course of the vehicle in substantial parallelism with a referencesurface.

Another object of the invention is to provide an automatically steeredself-propelled vehicle which can maintain its course in substantialparallelism with a reference surface independently of the distance thatsaid vehicle is from said reference surface.

According to the present invention, and with these objects in view, thepresent invention can be utilized with a wheeled vehicle having a frameand motor means on said frame for propeliing the vehicle at least in onedirection. Steering means on the frame is provided for steering saidvehicle so that the course of the vehicle is normally at leastsubstantially parallel to a reference surface. At least one transmitteris provided for transmitting a signal in the direction of the referencesurface and at least one receiver is provided for receiving thereflected signal from the reflecting surface when the vehicle deviatesfrom its normal course. Regulating means are connected to the receiverand to the steering means for generating a control signal in response tosaid reflected signal for activating said steering means when saidreflected signal is received by said receiver means to thereby alter thecourse of the vehicle and to cause the vehicle to resume its movement insubstantial parallelism with said reference surface.

According to a presently preferred embodiment, the receiver includes aplurality of receiver sensors arranged in a determined order withrespect to the transmitted signal. Each sensor is positioned to receivethe reflected signal for different relative orientations of the vehiclewith respect to the reference surface. The sensors are calibrated togenerate output sensor signals which are a function of the degree bywhich said vehicle alters its course from its normal course. The outputsensing signals generated by the sensors appear in quantized form andthese are converted in a digital-toanalog converter which is connectedto said sensors for converting said output sensing signals into ananalog output signal. A variable gain amplifier is provided which hasmeans for changing its gain. The amplifier is connected to thedigital-to-analog converter and to the steering means for amplifyingsaid analog output signai to yeild a control signal for appropriatelyactivating, at a predetermined distance of said vehicle from saidreference surface, said steering means. To make the control signalsindependent of the distance of the vehicle from the reference surface,the means for changing the gain includes a potentiometer having amovable portion, said analog output signal being applied across thepotentiometer and said amplifier input being connected to said movableportion. Position changing means are provided for changing the positionof the movable portion as a function of and proportional to the distancebetween the vehicle and the reference surface, whereby said controlsignal is substantially independent of the latter distance. In order tochange the distance of the vehicle from the reference surface, thewheels of the vehicle are rotatable from the normal position. Theposition changing means comprise a servo motor operatively connected tothe movable portion-to move its position when the servo motor isenergized. An AND control switch has an output and two input points andgenerates an output at said output point only when appropriate signalsare applied to both input points to energize said servo motor. One inputpoint of said control switch is connected to the steering control meansto sense the presence of the appropriate control signal. The other inputpoint is connected to a control device connected to the wheels to sensewhen the wheels are rotated 90 from their normal position and thevehicle is changing its distance with respect to the reference surface.In this manner, the movable portion position and the gain of theamplifier is changed only in relation to changes in distance of saidvehicle from said reference surface.

The novel features which are considered as characteristic for theinvention are set forth in particular in the appended claims. Theinvention itself, however, both as to its construction and its method ofoperation, together with additional objects and advantages thereof, willbe best understood from the following description of specificembodiments when read in connection with the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a schematic plan viewillustrating an area having obstructions, and a vehicle on theunobstructed portion of the area;

F IG. 2 is a schematic view illustrating an area having obstructionssurrounded by conductors, and a vehicle on the unobstructed portion ofthe area;

FIG. 3 is a schematic plan view of an automatically steeredself-propelled vehicle;

FIG. 4 is a diagram illustrating an electric circuit for the sensingmeans with which the vehicle of FIG. 3 is provided;

FIG. 5 is a diagram illustrating schematically the interconnectionbetween elements of the control device of the vehicle;

FIG. 6 is a diagram schematically illustrating the control of thesteering means of the vehicle; and

FIG. 7 is a schematic plan view of an automatically steeredself-propelled vehicle incorporating the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIG. 1, an area 10has obstructions'll and 12. A self-propelled vehicle 13, shown ingreater detail in FIG. 3, may carry rotary-sweeping brushes for cleaningthe unobstructed portion of the area 10. The obstructions 11 and 12project above the surface of the area, and would obstruct the movementof vehicle 13. The area 10 is surrounded by a suitable obstruction bywhich vehicle 13 is prevented from moving out of and beyond the area.

The vehicle 13 is placed at the region 14 of the surroundingobstruction, and is driven by a motor 47 driving wheels 48, to movealong a substantially straight path 14a shown with broken lines andarrowheads, until reaching the region 15 of the surrounding obstructionor boundary 22, which is recognized by front sensor means 16 of vehicle13. The front sensor means generate a reversing signal which causesreversing of motor 47 so that the vehicle 13 moves in a rearwarddirection along the path 15a back to the region 14 of the surroundingobstruction 22. The rear sensor 49 senses the position of the vehicle,and causes again reversing of motor 48, so that the vehicle is againdriven to move in forward direction toward the other end of the areaIt). The vehicle 13 includes a control device 46 in which the signalsgenerated by the sensing means 16 and 49 are evaluated for initiatingrequired operations. In the region 14, the steering means of the vehicleare operated under the control of the control device 46 to turn thewheels 48 a suitable angle, for example 90 or 45", to a new pathstarting at point 17. The distance between the first paths 14a and 15aand a new path may correspond to the width of vehicle 13 so that theentire area 10 would be successively swept by vehicle 13, if noobstructions l1 and 12 were found in area 10. The return of wheels 48 tothe normal position for forward and rearward movement, is effected byresilient means when the steering motor 50 is de-energized. The steeringmotor 50 drives, when energized, a spindle 51 by which a gear 52 isdisplaced for operating a linkage 52a by which the wheels 48 areangularly displaced, as shown in FIG. 3. Resilient means 94,95 connectedwith linkage 91 straighten wheels 48 out when steering motor 50 isde-energized, see FIG. 6.

Vehicle 13 moves now along a path 17a until the sensing means 16 sensethe obstruction 11, which causes reversal of motor 47 by the controldevice 46 so that vehicle 13 moves along the path 17b in a rearwarddirection toward point 17 where rear sensor 49 recognizes the boundary24, and causes reversal of motor 47. The steering means 50,5l,52,48 areagain operated to steer the vehicle to a new path 18a on which thevehicle moves in forward direction toward the obstruction 11. Uponapproaching the obstruction 11, the sensing means 16, which includes arow of sensors, recognizes that the obstruction 11 only partiallyprojects into the new path 18a. Since only a part of the row of sensors16 engage the obstruction, the row of front sensors 16 recognizes howfar obstruction 11 projects into the new path 18a. The motor of thevehicle 47 is reversed, the vehicle moves back in reverse directionalong the path 18b, and is automatically steered, in accordance with theinformation derived from the row of sensors 16, a smallertransversedistance to the new path 19a where the vehicle moves forwardto the point 19 just bypassing the lateral surface of obstructionn 11. Alateral sensor 20 having a projecting actuator 53, as shown in FIG. 3,preferably constructed as a microswitch, engages the lateral surface ofthe obstruction 11 and is closed, but when vehicle 13 has passed theobstruction 11, the sensor switch 20,53 is again released by the lateralsurface of obstruction 11 and the actuator 53 moves again transverselyto open switch 20. In this manner, information is transmitted to thecontrol device 46 that the obstruction 11 has been passed, and thecontrol device 46 energizes the steering motor 50 to steer the vehicle13 to a new path located. between the obstruction l1 and the surroundingobstruction 22, and the steering means is controlled to straighten outthe wheels 48 at the point 21 so that the vehicle moves in the initialforward direction, until the motor 47 is reversed at the boundaryobstruction, and vehicle 13 moves back until the rear sensor, also amicroswitch 49, again senses the obstruction 11 during rearward movementof vehicle 13.

As described above, motor'47 is again reversed and the steering meansoperated so that vehicle 13 moves along path 23a to the point 23 wheremotor 47 is reversed so that the vehicle moves rearward along path 23buntil the rear sensor 49 senses the obstruction 11, and causes steeringof vehicle 13 back to point 21, rearward toward obstruction 11, wherethe vehicle is steered again to move onto the track where it movesforwardly until reversed by the boundary obstruction 22 and moves alongthe path 19b to the other end of the area 10, where the movements of thevehicle 13 are-controlled as described above, and as shown in brokenlines provided with arrowheads in FIG. I. When vehicle 13 approaches thelateral boundary obstruction 22a, an end sensor 77 senses theobstruction 22a, and causes de-energization of motor 47 so that thevehicle stops, when the front sensor means 16 engages the other end ofthe boundary obstruction.

The embodiment of FIG. 1 operates due to mechanical operation of sensorswitches. However, if the obstructions are recesses in the surface ofthe area, as shown at 26,27, and 28, in FIG. 2, wire loops 29 and 30 areplaced on the surface of the area around the obstructions 26,27,28, andare connected to alternating current generators 31 and 32, as shown inFIG. 2. The corresponding loop 33 of a conductor may form the boundaryobstruction around the area 25, and is supplied by alternating currentgenerator 34 with a required current, so that the currents flowing inthe wire loops create alternating fields. The vehicle 13' is providedwith front sensors 78, lateral sensor 79, stop sensor 81, and rearsensor 80, each of which includes a coil responsive to the alternatingfields and controlling the reversing and steering operations of vehicle13'. The pattern according to which the area 25 is swept by the vehicle13', is the same as described with reference to FIG. ll.

Referring now particularly to FIG. 3, the forward end a of thesupporting frame 35 ofvehicle 13, carried microswitches 36 to 45arranged in a horizontal row, which either in the actuated condition, orin the normal position, generate a signal for the control device 46,which includes a storage device 76, as shown in the schematic diagram ofFIG. 5. The storage device 76 may consist of bistable multivibratorswhich store the width of the portion of the vehicle 13 which is stoppedby an obstruction. Each microswitch 36 to 45 is correlated with acertain information which is introduced into the control device 46 andthe storage device 76, so that the width of an obstruction can also bedetermined by the sensing means 36 to 45 when the obstruction is narrow,so that only one microswitch 41, for example, engages the obstruction,while the other microswitches 36-40 and 4245 are free. In accordancewith the signals from the sensing means, which indicate that anobstruction or obstacle is located in the path of movement of thevehicle 13, the electromotor 47, which is the drive motor of the vehicle13, is reversed. As explained above, the wheels 48 are then driven in areverse direction of rotation, and the movement of the vehicle 13 takesplace opposite to the intial forward direction. This rearward movementis maintained until the microswitch 49 at the rear end of frame 35senses an obstruction, and generates a signal which indicates that thevehicle 13 has arrived at the start of the respective path of movement.In accordance with the width of the obstacle determined by the frontsensor microswitches 36 to 45, vehicle 13 is moved laterally thedistance determined by the microswitches 36 to 45.

If the sensed obstruction is wider than the vehicle 13, which is thecase when the front sensor microswitches 36 to 45 engage the boundaryobstruction 22 at the end of a forward movement, the control device 46controls the steering means to move the vehicle in transverse directionits entire width.

When the lateral sensor 53 senses the end of a passed obstruction 11, itgenerates a signal to the control device 46, which causes a transversesteering of the vehicle 13 for its entire width in the same transversedirection in which sensor 53 projects, so that the vehicle can movebetween the front face of obstruction 11 and the boundary obstruction 22so that no part of the surface area is skipped.

FIG. 4 illustrates an electric circuit for the sensor microswitches 36to 45. Each microswitch 35 to 45 has a shiftable contact 54 to 63.Shiftable contacts of sensor switches, which are not actuated by anobstruction, are connected in series as shown for the shiftable contacts61,62,63 of the sensor switches 43,44,45. The seriesconnected contacts61,62,63 are connected to the positive terminal of a capacitor 74, whichis also connected to the base of an input transistor 73 of the controldevice 46. The microswitches, which engage an obstruction, for examplethe microswitches 37 to 42 in FIG. 4,

V displace the respective shiftable contacts 54 to 60 to positionsconnected with the resistors 64 to 72, respectively, which havedifferent resistances, which differ by the same amount. One free contactof microswitch 45, which is open, is connected to the interconnectedends of resistors 64 to 72, and to the negative terminal of capacitor74. Consequently, the input electrode of the input transistor 73receives an input signal corresponding to the charge of capacitor 74,and representing the width of the sensed obstruction 11.

Referring now to the schematic diagram of FIG. 5, the steering means,represented by refercncenumeral 50, are connected with the storagedevice 76 by an AND gate 75 which permits passage of a signal only whenan output signal is generated by rear sensor switch 49 together with asignal from storage means 76 for causing operation of the steering means50. The storage device 76, which may consist of multivibratorsrespectively correlated with the front microswitches 37, 35 isconstructed so that the multivibrators switch to one or the otherposition depending on the condition of the microswitches 36 to 45, andremain in the shifted condition until the vehicle 13 has been steeredinto the next path. Storage device 76 is connected with the frontsensing means 16 for recognizing the obstructions, which include theelectromechanical microswitches 36 to 45.

In accordance with the determined value corresponding to the width ofthe obstruction 11 or 12, drive motor 47 is reversed so that the vehiclemoves in the opposite direction until rear sensor switch 53 generates asignal .which causes again reversal of drive motor 47 withoutenergization of the same, as will be explained hereinafter. First, thesteering motor 50 is operated so that when drive motor 47 is againenergized, the vehicle 13 is steered laterally to the next followingpath. After the lateral displacement of vehicle 13, the wheels 46 areautomatically straightened so that vehicle 13 drives in a substantiallyforward direction until sensing another obstruction in its path,or'until arriving at the boundary obstruction 22.

By passing of an obstruction 11 or 12, the lateral sensor 53 generates asignal which influences the steering motor 50 to cause movement of thevehicle in the lat eral direction into the omitted part of the area. Theend switch 77 on the other side of the vehicle 13 is actuated whenengaging the lateral portion 22a of the boundary obstruction, anddisconnects drive motor 47 from the voltage source.

The storage 76 may be constituted by a capacitor, but it is alsopossible to provide a counting storage, as shown in FIG. 6. Such astorage 76 counts the actuated front sensor switches 36 to 45, and thecounted number of operated front sensing switches in stored, until nolonger required. Storage means of this type are well known to thoseskilled in the art.

Referring now to FIG. 6, three microswitches 36,37,38 are shown,respectively connected with resistors 64,65,66,as also shown in FIG. 4.Microswitches 36 to 45 can be connected by resistors 64 to 72 withstorage device 76 of the control device 46.

Switches 36 to 38, for example, are connected by a OR gate 83 with thewinding 84 of a relay. Relay 84 operates a reversing switch 85 which isalso operable by the rear sensor 49. Reversing switch 85 is connectedwith drive motor 47 for reversing the same, so that the motor 47 isreversed when front sensor switches 36,37,38 simultaneously abut theobstruction during forward movement, or when rear sensor 49 abuts theboundary obstruction during rearward movement of the vehicle 13. Thestop switch 77 is connected into the circuit of drive motor 4-7, so thatthe same is disconnected from the voltage source when the lateralboundary obstruction 22a is sensed by the sensor 77.

The storage means 76 is connected with the first input of an AND gate 75whose second input is connected with a contact of the reversing switch35. The output of the AND gate 75 is connected with the steering motor50. Storage means 76 is also connected with the first input of an ANDgate 38 at whose second input a voltage is applied, and whose thirdinput receives a signal from the lateral sensor switch 53. Adifferential element 96 connects lateral sensor switch 53 with the ANDgate 88, and has the effect that only when a signal is generated by thelateral sensor switch 53, a pulse opens the AND gate 88. The output ofthe AND gate 88 is connected with the steering motor 50 which, asexplained above, operates a worm spindle 85 and a gear segment 90 fordisplacing a steering link 91 by which the wheels 48 of the vehicle 13can be angularly displaced. The two springs 94 and 95 are acting onlink- 1 age 91 to turn wheels 48 to a straight position when motor 50does not operate.

When the vehicle 13 senses an obstruction during forward movement, atleast one of the front switches 36 to is actuated, so that a pulsereaches the winding 84 of the relay of the reversing switch 83 to the ORgate 83 so that drive motor 47 is reversed, causing the vehicle 13 tomove along the same path as before in the reverse opposite direction.The width of the obstruction is determined in the storage means 76 bythe number and position of the actuated front sensor switches 36 to 45.When vehicle 13 has arrived in its initial position, the rear sensor 49is operated by the boundary obstruction, so that the reversing switch 85is shifted and the drive motor 47 is set to forward movement. At themoment in which the rear sensor 49 responds, and reversing switch 85 isshifted, the voltage source of motor 47 is connected with the AND gate75 so that steering motor 51) is energized during a certain time inaccordance with the electric charge stored in storage means 76, forexample in a capacitor, the charge representing the width of theobstruction in the path of movement of the vehicle 13. The time duringwhich steering motor 511 is energized and turn wheels 48, is sodetermined that the wheels are turned 90, and the vehicle moves in adirection transverse to its previous direction of movement until, inaccordance with the amount of electricity stored in storage means 76,the AND gate 75 closes again so that steering motor is reset, andsprings 941,95 turn wheels 48 back to the initial straight position.

During the following movement of vehicle 13, the lateral sensor switch53 is depressed, and nothing happens because the differential element 97blocks the generated signal. When vehicle 13 has passed the obstruction,the actuator of the lateral sensor switch 53 is urged by a spring tomove outward again so that a pulse is transmitted through thedifferential element 96 to the AND gate 89 and opens the same so thatsteering motor 50 is then connected with the voltage, but in a differentpolarity, as compared with the operation when rear sensor 49 sensed therear portion of boundary obstructiOn 22. Consequently, wheels 48 areagain turned but in the opposite direction, so that the vehicle 13 moveslaterally, as viewed in FIG. 1 from the point 19 to the point 21 of itspath. After the vehicle 13 has moved transversely a distancecorresponding to the width of the obstruction 11, the AND gate 88closes, and steering motor 50 is no longer operated, so that springs 94and 95 turn wheels 43 back to a straight position for forward andrearward movement. At the same time when steering motor 50 isdisconnected, a signal may be transmitted to storage means 76 whichcauses clearing of storage means 76 since the signal stored in the sameis no longer required.

Paths 14a, 15a, 17a and so on have been shown in FIG. 1 to be straightpaths. As has been described, referring to FIG. 6, springs 94,95 areprovided which act on linkage 91 to turn the wheels 38 to a straightposition when motor 50 does not operate. This, at least to a firstapproximation, steers vehicle 13 in the substantially straight pathsshown in FIG. 1. However, as a practical matter, unevenness of theground over which vehicle 13 traverses, tolerances in the steeringlinkages and wheels of the vehicle and other prevailing influencessometimes have the tendency to cause vehicle 13 to move off of itspredetermined straight course despite the action of resilient means94,95.

Accordingly, the present invention is shown embodied on vehicle 13,where some of the details shown in FIG. 3 have been deleted for clarity.It should be noted, however, that the components shown in FIG. 3 are notnecessarily replaced by the apparatus to be described in relation toFIG. 7. This latter apparatus merely serves to assist or enhance theoperation of the vehicle 13 in substantial parallelism to a referencesurface as will hereinafter be described. Referring to FIG. 7, thereference surface 3 is shown from which vehicle 13 is spaced apredetermined amount, leaving a space 2 therebetween. On vehicle 13 ismounted transmitter means 164 and receiver means comprising of sensorsthrough 109. The transmitter 104 transmits a signal 4 in the directionof the reference surface 3, the signal reflected 5 being received by oneof the sensors 194 through 169. The type of signal transmitted bytransmitter 104i is not critical for the purposes of the presentinvention, any suitable signal commonly used for such purposes beingequally suitable. The only requirement, is that the reference surface 3be at least partially reflecting of the type of signal which istransmitted by 104 so as to give rise to a reflected signal 5. Thus,transmitted signal 41 can consist of electromagnetic radiation, such asa light beam. In such an instance, transmitter 104 would consist of alight source and sensors 1043 through 109 would consist ofphotodetecting devices. Another possibility is that transmitted signal 4be an acoustic signal, in which case transmitter 164 can be in the formof a loudspeaker while sensors 10 1 through 109 can be selected to be aplurality of microphones.

As shown in FIG. '7, the transmitter 104 and the receiver sensors 105through 109 are mounted on a rotatable deck 1 10. By such mounting, itis possible to rotate the direction of transmission of the transmitter104 and the receiver sensors 165 through 109 in such a way as to utilizeany surface surrounding vehicle 13 as a reference surface. As describedabove, space 2 can contain obstacles and as such, where appropriate, theelevation of the transmitter 104 and the sensors 105 through 109, shouldbe such that these obstacles would not interfere or obstruct thetransmitted signal 1 or the reflected signal 5.

The sensors 105 through 109 are arranged in a predetermined order withrespect to the transmitted signal, each sensor being positioned toreceive the reflected signal for a different relative orientation of thevehicle with respect to the reference surface. Normally, when thevehicle 13 is progressing along one of the straight paths depicted in F1G. 1 and substantially parallel to a reference surface such as surface22, the transmitted signal 4 is transmitted perpendicularly to thereference surface 4 and, therefore, the angle of incidence is zero.Since the angle of incidence is zero, the reflected signal returns alongthe same path as the transmitted signal traversed, and the reflectedsignal is detected by a neutral sensor, such as sensor 107. The effectof this will hereinafter be described. Now, should the vehicle 13deviate off its course of substantial parallelism with the surface 3,then, transmitter 104 being fixed to the frame of the vehicle 13, thetransmitted signal 4 will now impinge on the reference surface 3 at apredetermined incidence angle. Accordingly, the reflected signal 5 willno longer impinge on sensor 107 but on another sensor, such as sensor105, as shown in FIG. 7. The more the vehicle 13 deviates off its courseof substantial parallelism with the surface 3, the greater is the angleof incidence and said beam accordingly impinges on sensors further fromsensor 107. If the deviation of the vehicle 13 is in opposite direction,then the reflected signal 5 will impinge on a sensor on the other sideof neutral sensor 107, such a sensor 108 or 109. The sensors 105 through109 are calibrated to generate output sensing signals which are afunction of the relative position of the individual sensors in relationto sensor 107. Thus, according to one arrangement, the output sensingsignals of sensors 105 through 109 could increase in ascending order.However, the specific nature of the output sensing signals is notcritical as long as they contain the information regarding the deviationof the vehicle.

Since the sensor 105 through 109 are shown to be individual sensors,each sensor will, in response to impingement of the reflected signal 5on said sensor, generate a discrete output sensing signal. Statedanother way, the outputs of sensors 105 through 109 are quantized inamplitude, phase, or some other variable. According to the embodimentpresently shown in FIG. 7, the output sensing signals are quantized inamplitude and the quantized output sensing signals are fed to adigital-to-analog converter 100 for converting the output signals from aquantized signal to an analog signal. The analog output signal fromdigital-to-analog converter 100 is placed across potentiometer 111. Thepotentiometer 111 has a movable portion or a slidable contact which ismechanically connected to servomotor 11.3. The sliding contact of thepotentiometer 111 is electrically connected to the input of a variablegain amplifier 112, whose output is connected to the steering motor 50.

When the vehicle 13 is travelling at a predetermined distance from thereference surface 3, the transmitter 104 is intermittently orcontinuously transmitting the signal 4 at the reference surface 3. Aslong as the vehicle 13 progresses in substantial parallelism with thereference surface 3, the reflected signal 5 impinges on the sensor 107.The output sensing signal of the sensor 107 and the digital-to-analogconverter are so adjusted that when the reflected signal 5 impinges onthe neutral sensor 107, no control signal is supplied at the output ofamplifier 112 which energizes steering motor means 50 to modify thecourse of vehicle 13. However, should the vehicle 13 now deviate fromits course of substantial parallelism with the surface 3, the reflectedsignal will now impinge on a sensor other than the neutral sensor 107.Assuming that the reflected signal impinges on the sensor 106, a controlsignal will be generated at the output of the amplifier 112 to correctthe course of the vehicle 13. The amplitude of the control signal is afunction of the angle of incidence of the reflected signal, andtherefore upon which sensor the reflected signal impinges on. Forexample, should the reflected signal 5 impinge on the sensor instead ofthe sensor 106, then the control signal which energizes the steeringmotor 50 would be correspondingly greater, since the course of thevehicle 13 must be modified to a greater extent in order to maintain itsnormally defined course.

The calibration of the sensors 104 through 109 results in a set ofcontrol signals which are most appropriate for a predetermined distancebetween the vehicle 13 and the reference surface 3. It is clear from thegeometry that even for equal angles of incidence of the transmitted andreflected signals, the reflected signal 5 may impinge on a sensor closeror further from the neutral sensor 107 depending on the distance of thevehicle 13 from the reference surface 3. In order to maintain thecontrol signals only a function of the angle of incidence of thereflected signal 5 and not a function of the absolute distance of thevehicle 13 from the reference surface 3, means are provided foradjusting the gain of the amplifier 112 as a function of the distance ofthe vehicle 13 from the reference surface 3, so as to compensate for theabove-described fact. Thus, an AND control device, here shown as an ANDgate 120, is shown to have one output and two input points. The outputpoint of AND gate is connected to the servomotor 1 13 for energizing thesame under specified conditions. One input point of the AND gate 120 isconnected to the output of amplifier 112 to sense the presence of acontrol signal. The other input point of the AND gate 120 is connectedto the junction point between the motor 17 and the control device 46.With this arrangement, the output of AND gate 120 will energizeservomotor 113 only when both the wheels of the vehicle have turned 90to their normal direction and they are in fact turning. This conditionsignifies that the vehicle 13 is moving in a direction perpendicular tothe reference surface 3 in a way as to modify the distance between thereference surface 3 and the vehicle 13. For the duration of time thatthe wheels of the vehicle 13 are 90 from their normal position and thesewheels are turning, the output of AND gate 120 energizes the servomotor113 which is operatively connected to the movable portion or slidingcontact of the potentiometer 111. Thus, by ensuring that the vehicle 13moves towards or away from the reference surface 3 at a constantvelocity, and by ensuring that the servomotor 113 moves the slidingcontact at a correspondingly constant velocity, the position of asliding contact, and, there fore, the effective gain of amplifier 112can be proportionally changed. Now, the impingement of the re flectedsignal on one of the sensors 105 through 109,

llil

may not produce a control signal as large or as significant as they didat another prior distance. Although the output sensing signals of thesensors 105 through we in response to impingement thereon of thereflected signal remains substantially constant, a greater or lesserportion of the converted analog output signal is fed to the amplifier1112. In a sense, the gain adjusting means above described is not unlikea weighing factor which weighs the output sensing signals from therespective sensors to take into account the distance of the vehicle 13from the reference surface 3. By using such an arrangement, the controlsignals which energize the steering motor to modify slight deviations ofthe vehicle off its course of substantial parallelism, is substantiallyindependent of the distance of the vehicle 13 from the reference surface3 and almost entirely dependent on the degree of deviation from thedesired course.

It will be understood that each of the elements described above, or twoor more together, may also find a useful application in other types ofvehicles for automatically following an obstructed surface differingfrom the types described above.

While the invention has been described as embodied in an automaticallysteered self-propelled vehicle following its direction of movementautomatically in substantial parallelism with a reference surface, it isnot intended to be limited to the details shown, since variousmodifications and structural changes may be made without departing inany way from the spirit of the present invention.

Without further analysis, the foregoing will so fully reveal the gist ofthe present invention that others can by applying current knowledgereadily adapt it for various applications without omitting featuresthat, from the standpoint of prior art, fairly constitute essentialcharacteristics of the generic or specific aspects of this inventionand, therefore, such adaptations should and are intended to becomprehended within the meaning and range of equivalence of thefollowing claims.

What is claimed as new and desired to be protected by Letters Patent isset forth in the appended claims.

I claim:

1. An apparatus for maintaining a substantially fixed relativeorientation between at least one partially reflecting reference surfaceand a steered self-propelled vehicle, particularly a vehicle formovement over the unobstructed portion of an area having obstructions,comprising a vehicle frame; motor means on said frame for propellingsaid vehicle at least in one direction; steering means on said frame forsteering said vehicle so that the course of the vehicle is normally atleast substantially parallel to said reference surface; at least onetransmitter means for transmitting a signal in the direction of saidreference surface; at least one receiver means for receiving thereflected signal from said refleeting surface when said vehicle deviatesfrom said course; and regulating means connected to said receiver meansand to said steering means for generating a control signal in responseto said reflected signal for activating said steering means when saidreflected signal is received by said receiver means to alter the courseof the vehicle and cause the vehicle to resume its movement insubstantial parallelism with said reference surface, wherein saidreceiver means includes a plurality of receiver sensors arranged in apredetermined order with respect to the transmitted signal, each sensorof said receiver means being positioned to receive said reflected signalfor different relative orientations of said vehicle with respect to saidreference surface and being calibrated to generate output sensingsignals which are a function of the degree by which said vehicledeviates from its normal course.

2. An apparatus as defined in claim 1, further comprising sensing meanson said frame for generating a signal when sensing an obstruction duringmovement in said direction; and a control device including steeringcontrol means responsive to said latter signal of said sensing means tooperate said steering means to change the direction of movement of saidvehicle so that said vehicle continues to move on said unobstructedportion of said area.

3. An apparatus as defined in claim 11, further including rotatablemeans for supporting said transmitter and receiver means and forrotating said transmitter and receiver means in equal amounts inrelation to said vehi cle frame, whereby any surface surrounding saidvehicle can be chosen to be said reference surface.

4. An apparatus as defined in claim 1, wherein two transmitter means andtwo corresponding receiver means are arranged on said frame, eachtransmitter means transmitting a signal towards a correspondingreference surface.

5. An apparatus as defined in claim 1, wherein said transmitter andreceiver means comprise a light source and photo-electric meansrespectively, and said transmitter and reflected signals comprise lightbeams.

6. An apparatus as defined in claim 1, wherein said transmitter andreceiver means comprise acoustic transmitter and acoustic receiver meansrespectively, and said transmitted and reflected signals compriseacoustic signals.

7. An apparatus as defined in claim 1, wherein said output sensingsignals generated by said sensors appear in quantized form, and whereinsaid regulating means includes a digital-to-analog converter which isconnected to said sensors for converting said output sensing signalsinto an analog output signal.

8. An apparatus as defined in claim 7, wherein said regulating meansincludes a variable gain amplifier, having means for changing its gain,which is connected to said digital-to-analog converter and to saidsteering means for amplifying said analog output signal to yield saidcontrol signal for appropriately activating, at a predetermined distanceof said vehicle from said reference surface, said steering means.

Q. An apparatus as defined in claim 8, wherein said means for changingthe gain includes a potentiometer having a movable portion, said analogoutput signal being applied across the potentiometer and said amplifierinput being connected to said movable portion.

10. An apparatus as defined in claim 9, further comprising positionchanging means for changing the position of said movable portion as afunction of and proportional to the distance between said vehicle andsaid reference surface, whereby said control signal is substantiallyindependent of the latter distance.

ll 1. An apparatus as defined in claim 10, wherein said wheels of saidvehicle are rotatable from their normal position in response to anappropriate control signal to thereby enable the vehicle to move in adirection perpendicular to said reference surface to thereby change itsdistance relative to said surface, and wherein said position changingmeans comprises a servomotor operatively connected to said movableportion to move a control device and said motor means to sense when thewheels are energized to thereby detect when the vehicle is changing itsdistance with respect to said reference surface, whereby said movableportion position and the gain of the amplifier is changed only inrelation to changes in distance of said vehicle from said referencesurface.

1. An apparatus for maintaining a substantially fixed relativeorientation between at least one partially reflecting reference surfaceand a steered self-propelled vehicle, particularly a vehicle formovement over the unobstructed portion of an area having obstructions,comprising a vehicle frame; motor means on said frame for propellingsaid vehicle at least in one direction; steering means on said frame forsteering said vehicle so that the course of the vehicle is normally atleast substantially parallel to said reference surface; at least onetransmitter means for transmitting a signal in the direction of saidreference surface; at least one receiver means for receiving thereflected signal from said reflecting surface when said vehicle deviatesfrom said course; and regulating means connected to said receiver meansand to said steering means for generating a control signal in responseto said reflected signal for activating said steering means when saidreflected signal is received by said receiver means to alter the courseof the vehicle and cause the vehicle to resume its movement insubstantial parallelism with said reference surface, wherein saidreceiver means includes a plurality of receiver sensors arranged in apredetermined order with respect to the transmitted signal, each sensorof said receiver means bEing positioned to receive said reflected signalfor different relative orientations of said vehicle with respect to saidreference surface and being calibrated to generate output sensingsignals which are a function of the degree by which said vehicledeviates from its normal course.
 2. An apparatus as defined in claim 1,further comprising sensing means on said frame for generating a signalwhen sensing an obstruction during movement in said direction; and acontrol device including steering control means responsive to saidlatter signal of said sensing means to operate said steering means tochange the direction of movement of said vehicle so that said vehiclecontinues to move on said unobstructed portion of said area.
 3. Anapparatus as defined in claim 1, further including rotatable means forsupporting said transmitter and receiver means and for rotating saidtransmitter and receiver means in equal amounts in relation to saidvehicle frame, whereby any surface surrounding said vehicle can bechosen to be said reference surface.
 4. An apparatus as defined in claim1, wherein two transmitter means and two corresponding receiver meansare arranged on said frame, each transmitter means transmitting a signaltowards a corresponding reference surface.
 5. An apparatus as defined inclaim 1, wherein said transmitter and receiver means comprise a lightsource and photo-electric means respectively, and said transmitter andreflected signals comprise light beams.
 6. An apparatus as defined inclaim 1, wherein said transmitter and receiver means comprise acoustictransmitter and acoustic receiver means respectively, and saidtransmitted and reflected signals comprise acoustic signals.
 7. Anapparatus as defined in claim 1, wherein said output sensing signalsgenerated by said sensors appear in quantized form, and wherein saidregulating means includes a digital-to-analog converter which isconnected to said sensors for converting said output sensing signalsinto an analog output signal.
 8. An apparatus as defined in claim 7,wherein said regulating means includes a variable gain amplifier, havingmeans for changing its gain, which is connected to saiddigital-to-analog converter and to said steering means for amplifyingsaid analog output signal to yield said control signal for appropriatelyactivating, at a predetermined distance of said vehicle from saidreference surface, said steering means.
 9. An apparatus as defined inclaim 8, wherein said means for changing the gain includes apotentiometer having a movable portion, said analog output signal beingapplied across the potentiometer and said amplifier input beingconnected to said movable portion.
 10. An apparatus as defined in claim9, further comprising position changing means for changing the positionof said movable portion as a function of and proportional to thedistance between said vehicle and said reference surface, whereby saidcontrol signal is substantially independent of the latter distance. 11.An apparatus as defined in claim 10, wherein said wheels of said vehicleare rotatable 90* from their normal position in response to anappropriate control signal to thereby enable the vehicle to move in adirection perpendicular to said reference surface to thereby change itsdistance relative to said surface, and wherein said position changingmeans comprises a servomotor operatively connected to said movableportion to move its position when said servomotor is energized; an ANDcontrol switch having an output and two input points and which generatesan output at said output point only when appropriate signals are appliedto both input points to energize said servomotor, one input point ofsaid control switch being connected to said steering control means tosense the presence of said appropriate control signal, the other inputpoint being connected to a control device and said motor means to sensewhen the wheels are energized to thereby detect when the vEhicle ischanging its distance with respect to said reference surface, wherebysaid movable portion position and the gain of the amplifier is changedonly in relation to changes in distance of said vehicle from saidreference surface.